This invention relates to a water pump and, in particular, a water pump that is disposed in a cooling passage that provides cooling for an internal combustion engine.
Many different types of such water pump have been proposed. One such pump has the cooling passage formed by combining a pump casing with a pump cover. An example is the water pump disclosed in Japanese unexamined publication (koukai)11-125118. There the water pump includes a plate that is disposed for dividing a water circulation cavity into an inlet passage and an outlet passage. The plate is formed of a thin metal material and is disposed between the pump casing and the pump cover. However, if a force holding the plate in position is weak, it is possible for a gap to occur between the pump casing, the pump cover, and the plate. In such case, the plate can not divide the outlet passage from the inlet passage. For example, a difference in a pressure between the inlet passage and the outlet passage causes the coolant to leak within the water circulation cavity between the inlet passage and the outlet passage. Namely, the coolant flowing in the outlet passage might leak to the inlet passage through the gap. As a result, the leakage reduces the efficiency of the pump.
It is, therefor, a principal object of this invention to provide an improved and high efficiency water pump for an internal combustion engine that prevents leakage in the water circulation cavity.